repeat array going up and down in with some limit

Question

I have data in this form [1,2,3,4]. I want to perform some operation on this array so that I will get output like this [1,2,3,4, 4,3,2,1, 1,2]. Please, can you suggest some way for me to achieve this output?

// function declaration 

function arrayExm(array,limit){ 
  // want some operations here so that i will get this output
}

//function execution 

arrayExm([1,2,3,4],10) 
//so it will return [1,2,3,4, 4,3,2,1, 1,2]

Answer 1

You can achieve it using a simple for loop.

function arrayExm(array, limit) {
  var res = [],
    len = array.length;

  // iterate upto the limit
  for (var i = 0; i < limit; i++) {
    // define the value based on the iteration 
    res[i] = Math.floor(i / len) % 2 == 0 ? // check the array element repetition is odd or even
      array[i % len] : // if even define element in same order   
      array[len - i % len - 1]; // if odd define element in reverse order
  }

  return res;
};



console.log(arrayExm([1, 2, 3, 4], 10))